tangent: The Harry Potter thing you mentioned is made even more blatant by the film tossing out the entirely necessary exposition in favor of a melodramatic Neville speech (book defiance: two lines, movie defiance: STOP TALKING ALREADY) and then making Harry and Voldemort's last "fight" an asinine shakycam clusterfuck.
back to topic:
Choice doesn't necessarily have to be the thing that makes a game a game. Half-life as a whole has basically no choice on the part of the player beyond 'keep following the plot,' but in a weird way that's why it works as a game- the player has about as much control of the situation as Gordon does. Same with Bioshock and Infinite (both of which were devilishly meta about it).
Similarly, there are a lot of games that would just not work in any other medium- Journey, for example, is half interactive art-piece and half adventure game thing. And there's not much in the way of challenge in it, but it's still fascinating to play. Same with To The Moon.
I had a lot of rambling thoughts that made no sense when typed, but in short- presentation matters. To make a dated reference, I know [a game] when I see it.